/**
*      author: Y_Yao
*      created: 2025-02-22 20:02:01
**/

#include<bits/stdc++.h>

#define int LL
using namespace std;
using LL = long long;
const LL LLINF = 1e18;
const int INF = 0x3f3f3f3f;
const int N = 50 + 7;
vector<string> a;
int n;

bool cmp(string& s1,string& s2)
{
    return s1.size() < s2.size();
}

void solve()
{
    cin >> n;
    for(int i = 1;i <= n;i++)
    {
        string s;
        cin >> s;
        a.push_back(s);
    }
    sort(a.begin(),a.end(),cmp);
    for(auto& e : a)
    {
        cout << e;
    }
}

signed main()
{
    ios::sync_with_stdio(false);
    cin.tie(0);

    int t = 1;
    //cin >> t;
    while(t--)
    {
        solve();
    }
    return 0;
}